Directional signal beacon

ABSTRACT

A directional traffic signal beacon having a converging lens at the signal face illuminated by a light source reflected toward the lens through a mosaic of condenser lenses and a field aperture adjustable as to both size and shape by means of movable shutter elements disposed in the focal plane of the lens to predetermine the field of view from which the signal indication is visible. The shutter elements are spherical segments conforming in curvature to the focal plane and frictionally maintained in selected positions by spring-biasing members enabling manual arrangement of the shutter elements to define the field of view.

United States Patent 1191 Beck et a1.

1 1 Nov. 26, 1974 1 1 DIRECTIONAL SIGNAL BEACON [73] Assignee: The Singer Company, Binghamton,

22 Filed: July 2,1973

21 App1.No.:376,098

[52] US. Cl 240/41.3, 240/4601, 240/4613,

240/4659, 340/84, 340/383 [51] Int. Cl. F2lv 13/04 [58] Field of Search 240/22, 41, 41.1, 41.3

3,296,923 l/l967 Miles 353/38 3,371,202 2/1968 Moore et a1. 240/4613 X 3,457,400 7/1969 Appeldorn 240/4659 X 3,513,306 5/1970 Vantine 240/413 3,541,323 11/1970 Stewart et a1 240/4601 Primary Examiner-Samuel S. Matthews Assistant Examiner-Alan Mathews Attorney, Agent, or Firm-James C. Kesterson; .1. Ronald Richbourg [5 7] ABSTRACT A directional traffic signal beacon having a converging lens at the signal face illuminated by a light source reflected toward the lens through a mosaic of condenser lenses and a field aperture adjustable as to both size and shape by means of movable shutter elements disposed in the focal plane of the lens to predetermine the field of view from which the signal indication is visible. The shutter elements are spherical segments conforming in curvature to the focal plane and frictionally maintained in selected positions by springbiasing members enabling manual arrangement of the shutter elements to define the field of view.

11 Claims, 3 Drawing Figures PATENTE HUVZBISH sum 1 M 2 BACKGROUND'OF THE INVENTION 1. Field of the Invention This invention relates to signal beacons and more particularly to automobile and pedestrian traffic signals having a directional characteristic enabling their indications to be seen from selected viewpoints only.

2. Description of the Prior Art In the past signal beacons, or traffic signal lights, have been employed which display scintillating light, or light which has a sparkling appearance. Both pedestrians and vehicle operators have become accustomed to this form of signal beacon. As traffic problems become more complex with the larger number of vehicles on the road, it was necessary to employsignal beacons which were indicative of vehicle movement within a particular lane of traffic. For example, a green arrow has been employed for such intersection signal lights as right turns, left turns, etc. The red light associatedwith the green arrow has normally been nondirectional (i.e., it has simply been a standard red signal light). This situation can be ambiguousto pedestrians and vehicle operators who view simultaneously a red light for a left turn lane and a green light for straight through traffic. A solution to this problem has been the development of signal beacons which are directed for viewing from limited points, such as a left turn lane.

A prior art device having directional characteristics is disclosed in US. Pat. No. 3,457,400, entitled Apparatus and Method for Directing aBeacon Toward a Limited Viewing Area. The device constructed and' marketed in accordance with this patent employs a masking screen within the signal beacon for directing light to limited viewing screens. A diffuser is disposed within the beacon for distributing light over the surface of the lens. An apparent problem with this prior art device is that the light emitted appears flat to the viewer, which is not similar in appearance to conventional signal beacons. Also, there is a problem with the light gradually dimming as a viewer moves off axis. Stillanother disadvantage of this device is that special lamps are required which are distinctly different and more expensive than the lights employed in conventional traffic signal beacons.

The device of the present invention overcomes and mitigates the disadvantages of the prior art signal beacons as will be disclosed in greater detail hereinbelow.

SUMMARY OF THE INVENTION The present invention contemplates a directional signal beacon comprising a converging lens with a light source disposed substantially coaxially with the lens, and at a distance greater than the focal length of the lens. Additionally, a light reflection means is disposed adjacent to the light source, and is formed for directing the light towards the lens. A lenticulated light transmissive screen, or mosaic of condenser lenses. is disposed betweenthe light source and the focal plane of the lens. Also, an adjustable means for defining an aperture is disposed in the vicinity of the focal plane of the lens.

It is an object of this invention to provide a directional signal beacon which .closely approximates the ap- 'pearance of. more conventional traffic signal beacons.

It is another object of this-invention to provide a directional signal beacon which is readily programmable without the use of special tools and equipment.

A still further object of this invention is to provide a directional signal beacon which maintains substantially continuous brightness of light as the viewer shifts off axis.

Still another object of this invention is to provide a directional signal beacon which uses the same type of lamps as that employed in conventional signal beacons.

A feature of this invention resides in the provision of a mosaic of condenser lenses for producing scintillating light substantially the same as that produced by conventional signal beacons. Another feature of this invention resides in the provision of a unique reflector, elliptical in cross section, which improves light intensity at the outer extremities of the field of view.

Other objects and features of this invention will become apparent in the details and arrangement of its parts and in the combination thereof, reference being had to the following description of the preferred embodiment and accompanying drawings for a full description and illustration of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal axial section through a directional signal bea'con embodying the present invention;

FIG. 2 is a transverse sectional view of line 2-2 of FIG. 1 looking in the direction of the arrows; and

FIG. 3 is a detail sectional view on line 3-3 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings and first in particular to FIG. 1, a signal head 10 has a. generally elongate housing 12. A converging lens 14 is attached to one end of the housing 12. The lens 14 may be a fresnel lens for collecting light directed towards the lens. A fresnel lens is a relatively thin short focus condenser lens consisting of a series of concentric stepped rings, each one sub stantially conforming to a section of a convex surface. The combined effect of all 'the rings is the same as that of a single lens of normal shape with the same diameter and curvature. The effect of this lens is to collimate light impinging on the surface thereof. The surface having the stepped rings is preferably arranged outwardly of the signal beacon to avoid excessive light scattering within the beacon, and to keep this surface clean.

The principal point of focus 15 of the lens 14 is located along an optical axis 16 at a distance F from the lens. The plane of best focus or focal plane of the lens 14, which is defined as the surface upon which an axial image transmitted by the lens is brought to sharpest focus, is defined by an are 17 having a radius R. The distance R is preferably selected to be approximately one half of the distance F. In accordance with the preferred embodiment, which was reduced to practice, the distance F is equal to l 1 inches and the distance R is equal to 5-1/16 inches.

A color filter 18 is disposed in front of the lens 14, which may be red, yellow, green, etc., depending upon the use of the signal beacon. A light source 19 is disposed beyond the end of the housing 12 opposite to the lens 14, and aligned coaxially therewith along the optical axis 16 at a distance greater than the focal length F. A source of electrical power is provided via wires 20 to source 19 in a conventional manner. In accordance with the preferred embodiment, light source 19 is a conventional 150 watt traffic signal lamp. A reflector 21, which is elliptical in cross section, is disposed for supporting light source 19 and for directing light in a direction towards the lens 14. Preferably, filament 22 of the light source 19 is located at the focus of the ellipse formed by reflector 21. The result of using a reflector elliptical in cross section is that the light from source 19 may be focused at a point 23 along the optical axis 16. It is to be noted that the point 23 coincides with the second focus of the complete ellipse of which reflector 21 partially forms. The location of focus point 23 behind lens 14 (or at the second focus of the complete ellipse) eliminates a problem encountered in signal beacons, wherein the light from the beacon ostensibly shifts sidewardly in a direction opposite to the sideward movement of a viewer. More particularly, if the light from reflector 21 were focused at a point along the optical axis 16 and coinciding with the position of the lens 14, or at a position in front of the lens, then the light from the beacon would appear to shift sidewardly in a direction opposite to a sideward movement of the viewer. Therefore, the geometrical shape of the elliptical reflector 21 is important. According to the preferred embodiment of a beacon having a twelve inch diameter for lens 14, the major axis of the ellipse should be 14.125 inches, and the minor axis thereof should be 10.312 inches.

In accordance with a well-known principal of geometry, light rays emanating from one focus of an ellipse will pass through the second focus thereof. By way of example, light rays 24, which emanate from light source 19, pass through point 23.

A scintillating screen 25, or more particularly a mosaic of condenser lenses, is disposed in front of reflector 21 for forming a multiplicity of discrete light points. Screen 25 is an approximation of a lens screen, or mosaic of condenser lenses, similar to that disclosed in US. Pat. No. 2,183,249 entitled Illuminating Device for Projectors. In accordance with the directional signal beacon which was reduced to practice, a satisfactory approximation of a mosaic of condenser lenses was made by uniformly stippling both sides of a flat glass plate. The overall result from employing a mosaic of condenser lenses in the preferred embodiment was to produce lighting having a scintillating appearance.

Screen 25 is preferably located away from the focal point in order that the multiplicity of light points produced by the screen will appear as a multiplicity of out-of-focuslight points to the observer. More particularly, the out-of-focus light points constitute discrete facets of the scintillating light emitted by the beacon 10. Screen 25 is located at a distance d, along the optical axis, from the point 15 in a direction away from lens 14. In accordance with the preferred embodiment, which was reduced to practice, distance d was 1.50 inches.

At this juncture of the description, a fundamental distinction between the device of the present invention and that of the prior art device (i.e., US. Pat. No. 3,457,400) is pointed out. The prior art device employs a diffuser, which is an optical device for obtaining diffuse illumination. Diffuse illumination results when light strikes an irregular surface such as a frosted window or the surface of a frosted or coated lightbulb. When light is diffused, no definite'image is formed. More particularly, when diffusion is complete, a sharp image of the light source can no longer be seen; and its place is taken by a uniform, extended source which emits light in all directions.

In contrast, the device of the present invention employs a mosaic of condenser lenses which generate a multiplicity of images of the light source. If the mosaic employed in the present invention were placed at the focal point 15, a few discrete light points would appear to emanate from the beacon 10. This condition is not satisfactory since it does not simulate a conventional signal beacon having scintillating light. Therefore, a more satisfactory result was accomplished by moving the screen 25 out of focus. That is, the screen 25 was displaced from focal point 15, along the optical axis 16, by the distance d.

A shutter mechanism 26 is disposed along the optical axis 16 between the screen 25 and the lens 14 for forming an aperture which restricts light to a limited field of view. The shutter mechanism 26 is constructed of a partial hemispherical member 28 substantially conforming in curvature to the focal plane defined by are 17. The member 28 has an opening 30 therein. Four movable spherical segments 32, 33, 34, and are frictionally maintained in selected position by spring biasing mechanisms 38. Adjustment of spherical segments 32 through 35 may be made in such a manner as to form a restricted opening for defining the field of view of light from source 19. The shutter mechanism 26 will be explained in greater detail hereinbelow with the description accompanying FIGs. 2 and 3.

At this juncture of the description, the advantage of using an elliptical reflector 21 is pointed out. High intensity light may be directed onto a large surface area such as lens 14. Dashed lines 41 define the clearance envelope within which light from reflector 21 is directed onto the lens 14. When spherical segments 32 through 35 are removed, light from the reflector 21 is restricted by the size of the opening 30. However, with segments 32 through 35 adjusted to the position as shown in FIG. 1, light from reflector 21 is restricted to the smaller size of the opening 40.

Scattered light, which normally occurs within many optical devices, is reduced to a minimum by painting the surface of hemispherical member 28, spherical segments 32 through 35, and the inside of housing 12 flat black. Also, scattered light is further obstructed by arranging a plurality of baffles 42, which are annular in shape, along the inner walls of the housing 12. The inside diameter of baffles 42 conforms to the outer extremeties of the light clearance envelope defined by dashed lines 41.

Referring now to FIG. 2, a transverse sectional view of the shutter mechanism 26 is illustrated in greater detail. l-Iemispherical member 28 has an opening 30 therein, and provides a support surface for segments 32 through 35. Spring biasing mechanisms 38 frictionally maintain segments 32 through 35 in selected positions. More particularly, each segment may be moved to a desired position to modify the shape of the aperture 40 formed thereby.

With reference to FIG. 3, a detailed sectional view of the line 3-3 of FIG. 2 illustrates the spring biasing mechanism 38 in greater detail. A spring strap 44 is formed substantially in the shape of a trianglewith a first end 440 of the strap overlapping beyond the intersection point with the second end 44b of the spring strap. A hole 45 is formed in the first end 44a of the strap 44 for receiving an internal thread tubular rivet 46 such as a RlVNUT manufactured by the B. F. Goodrich Company of Akron, Ohio. However, other types of threads may be used which are recessible into the strap 44. Assuming a RIVNUT is employed herein, a thread thumb screw 43 is inserted within the tubular rivet 46. The portion of thumb screw 48 extending beyond strap 44 makes contact with one of the segments 32 through 35. It may be readily seen from the discussion hereinabove that by loosening the thumb screw 48 for each of the spring biasing mechanisms 38 the segments 32 through 35 may be positioned in such a manner as to form an aperture 40 of the desired shape and size. Following this, the thumb screw 48, for each of the biasing mechanisms 38, are twisted sufficiently to frictionally maintain the segments 32 through 35 at the desired position. Additional turns of the thumbscrew 48 will cause strap 44 to engage end 44b thereof, and greater pressure is exerted on the spherical segments. Therefore, it may also be readily seen that no special tools or equipment are needed to form an aperture of desired size and shape.

Accordingly, it may be seen from the discussion hereinabove that the advantage gained by using the shutter mechanism 26 having parts substantially conforming in curvature to the focal plane of the lens 14 are as follows. The edges of the field of view defined by the size and shape of aperture 40 are sharp. That is, a viewer will see a distinct cutoff of light as he moves a short distance from within to without the field of view. Also, the field of view may be aligned along an axis which is not coaxial with the optical axis 16, while maintaining all the features and advantages of this invention. More particularly, a field of view may be defined by aperture 40, which is off axis with that of the beacon l0; and the beacon need not be rotated or tilted on the signal head. Another advantage gained by defining the field of view with a shutter mechanism as disclosed herein is that there is no glass or other material in the focal plane which needs cleaning. That is, the aperture 40 has no material therein which may get dirty since it is truly an aperture.

The geometrical shape of the elliptical reflector 2i, and its position with respect to the focal plane as defined by are i7. and fresnel lens 14 is important. The elliptical reflector is an efficient collector of radiant energy and in this case isused to collect and direct the light from filament 22 through screen 25, through opening 30 and thence to lens 14.

The elliptical reflector 21 in the absence of the screen 25, directs light through opening 30 in such a way that every point on opening 30 is illuminated with light that also goes through lens 14. In this case the second focus of elliptical reflector 21, has been empirically placed at point 23, in order to obtain the effects described hereinabove. The introduction of screen 25 then will produce a scintillating appearance to the beacon. Also, as disclosed in US. Pat. NO. 2,183,249, it will redistribute the light transmitted to lens 114 such that light from each point on opening will flood lens 14.

It is obvious to one having ordinary skill in the art to employ a light dimming circuit in conjunction with a signal beacon as disclosed hereinabove for controlling the intensity of the signal light as a function of background light. One such circuit which may be employed for this purpose is an Extended Range Variable Voltage Circuit as manufactured by General. Electric Company, Model No. SlOOCl or Model No. SlOOCS. in conjunction with a conventional light sensor or photocell.

While a specific embodiment of the present invention has been shown and described hereinabove. modifications and improvements will occur to those skilled in the art. It is requested that one understand. therefore, that this invention is not limited to the preferred embodiment disclosed, and it is intended that the appended claims embrace all modifications which do not depart from the spirit of this invention.

What is claimed is:

l. A signal beacon having a predetermined field of view comprising:

a converging lens mounted within an opening of a support housing, said lens having a predetermined focal plane which includes a focus point along the optical axis of said lens at a known distance from said lens;

a light source positioned substantially on said optical axis of said converging lens and spaced at a distance from said lens greater than said known distance;

light reflecting means positioned on said optical axis suchthat said light source is located between said reflecting means and said lens for directing illumination reflected from said reflecting means parallel with said optical axis and toward said converging lens;

shutter mechanism located between said lens and said light source defining an aperture for control ling the area of said converging lens receiving reflected illumination from said light reflecting means; and

a lenticulated light-transmissive surface spaced between said shutter mechanism and said light source along said optical axis at a distance greater than said known distance for producing a multiplicity of light points such that said directional signal beacon provides a scintillating appearance within a predetermined field of view.

2. The apparatus of claim ll, wherein said aperture defined by said shutter mechanism is in said focal plane.

3. The signal beacon of claim ll, wherein said lenticulated lighttransmissive screen comprises a flat glass plate having a multiplicity of condenser lenses disposed in a uniform array on one side thereof.

4. The signal beacon of claim ll, wherein said shutter mechanism hasa curved configuration which substantially conforms with said focal plane of said lens.

5. A signal beacon according to claim 1 wherein said aperture-defining means is adjustable to vary size and configuration of the aperture.

6. A signal beacon according to claim 1 wherein said lenticulated light transmissive screen comprises a flat glass plate having a multiplicity of condenser lenses disposed in a uniform array on both sides thereof.

7. A signal beacon according to claim 4 wherein said light reflection means is an elliptical reflector.

8. A signal beacon according to claim 7 wherein said light source is disposed at a first focus of the ellipse formed by said reflector for directing light through the second focus of said ellipse.

9. A signal beacon having a predetermined field of view comprising:

a converging lens mounted within an opening of a support housing, said lens having a predetermined focal surface which surface includes a focus point along the optical axis of said lens at a known distance from said lens;

- a light source positioned substantially on said optical axis of said converging lens and spaced at a distance from said lens greater than said known distance;

light reflecting means positioned on said optical axis such that said light source is located between said reflecting means and said lens to direct illumination reflected from said reflecting means parallel with said optical axis and toward said converging lens;

shutter mechanism having a curved configuration and defining an aperture, said shutter mechanism located between said lens and said light source such that said curved configuration substantially conforms to said focal plane of said lens; and

a lenticulated transmissive screen spaced between such shutter mechanism and said light source along said optical axis at a distance greater than said known distance for producing a multiplicity of light points such that said directional signal beacon provides a scintillating appearance within a predetermined field of view.

10. The apparatus of claim 9 wherein said curved configuration of said shutter is substantially hemispherical and further includes:

a plurality of spherical segments slidably mounted on said hemispherical member for defining the size and shape of said aperture; and

spring-biasing means disposed adjacent said spherical segments for frictionally maintaining the position of said segments.

111. A signal beacon according to claim 9 wherein said lenticulated, light-transmissive screen is a mosaic 

1. A signal beacon having a predetermined field of view comprising: a converging lens mounted within an opening of a support housing, said lens having a predetermined focal plane which includes a focus point along the optical axis of said lens at a known distance from said lens; a light source positioned substantially on said Optical axis of said converging lens and spaced at a distance from said lens greater than said known distance; light reflecting means positioned on said optical axis such that said light source is located between said reflecting means and said lens for directing illumination reflected from said reflecting means parallel with said optical axis and toward said converging lens; shutter mechanism located between said lens and said light source defining an aperture for controlling the area of said converging lens receiving reflected illumination from said light reflecting means; and a lenticulated light-transmissive surface spaced between said shutter mechanism and said light source along said optical axis at a distance greater than said known distance for producing a multiplicity of light points such that said directional signal beacon provides a scintillating appearance within a predetermined field of view.
 2. The apparatus of claim 1, wherein said aperture defined by said shutter mechanism is in said focal plane.
 3. The signal beacon of claim 1, wherein said lenticulated lighttransmissive screen comprises a flat glass plate having a multiplicity of condenser lenses disposed in a uniform array on one side thereof.
 4. The signal beacon of claim 1, wherein said shutter mechanism has a curved configuration which substantially conforms with said focal plane of said lens.
 5. A signal beacon according to claim 1 wherein said aperture-defining means is adjustable to vary size and configuration of the aperture.
 6. A signal beacon according to claim 1 wherein said lenticulated light transmissive screen comprises a flat glass plate having a multiplicity of condenser lenses disposed in a uniform array on both sides thereof.
 7. A signal beacon according to claim 1 wherein said light reflection means is an elliptical reflector.
 8. A signal beacon according to claim 7 wherein said light source is disposed at a first focus of the ellipse formed by said reflector for directing light through the second focus of said ellipse.
 9. A signal beacon having a predetermined field of view comprising: a converging lens mounted within an opening of a support housing, said lens having a predetermined focal surface which surface includes a focus point along the optical axis of said lens at a known distance from said lens; a light source positioned substantially on said optical axis of said converging lens and spaced at a distance from said lens greater than said known distance; light reflecting means positioned on said optical axis such that said light source is located between said reflecting means and said lens to direct illumination reflected from said reflecting means parallel with said optical axis and toward said converging lens; shutter mechanism having a curved configuration and defining an aperture, said shutter mechanism located between said lens and said light source such that said curved configuration substantially conforms to said focal plane of said lens; and a lenticulated transmissive screen spaced between such shutter mechanism and said light source along said optical axis at a distance greater than said known distance for producing a multiplicity of light points such that said directional signal beacon provides a scintillating appearance within a predetermined field of view.
 10. The apparatus of claim 9 wherein said curved configuration of said shutter is substantially hemispherical and further includes: a plurality of spherical segments slidably mounted on said hemispherical member for defining the size and shape of said aperture; and spring-biasing means disposed adjacent said spherical segments for frictionally maintaining the position of said segments.
 11. A signal beacon according to claim 9 wherein said lenticulated, light-transmissive screen is a mosaic of condenser lenses. 